Abstract

Objective

To assess gastric trocarization and orogastric tubing as a means of gastric decompression for the initial management of gastric dilatation-volvulus.

Methods

Retrospective review of 116 gastric dilatation-volvulus cases from June 2001 to October 2009.

Results

Decompression was performed via orogastric tubing in 31 dogs, gastric trocarization in 39 dogs and a combination of both in 46 dogs. Tubing was successful in 59 (75·5%) dogs and unsuccessful in 18 (23·4%) dogs. Trocarization was successful in 73 (86%) dogs and unsuccessful in 12 (14%) dogs. No evidence of gastric perforation was noted at surgery in dogs undergoing either technique. One dog that underwent trocarization had a splenic laceration identified at surgery that did not require treatment. Oesophageal rupture or aspiration pneumonia was not identified in any dog during hospitalization. No statistical difference was found between the method of gastric decompression and gastric compromise requiring surgical intervention or survival to discharge.

Clinical Significance

Orogastric tubing and gastric trocarization are associated with low complication and high success rates. Either technique is an acceptable method for gastric decompression in dogs with gastric dilatation-volvulus.

After a presumptive diagnosis of GDV, management is initially aimed at intravenous fluid resuscitation and gastric decompression. Gastric distension leads to increased intra-abdominal pressure, which results in compression of the caudal vena cava, portal vein and splanchnic vasculature. This gives rise to poor venous return and splanchnic pooling, which causes a reduction in preload and ultimately a decrease in cardiac output and systemic blood pressure (Rasmussen 2003, Baltzer et al. 2006). Aggressive intravenous fluid therapy using both crystalloids and colloids is utilized to stabilize systemic blood pressure and improve tissue perfusion and oxygenation.

Once vascular access has been established and fluid resuscitation initiated, gastric decompression is performed. Described techniques of gastric decompression include orogastric tubing and gastric trocarization (Hedlund & Fossum 2007). Once gastric distension is relieved and intra-abdominal pressure decreases, venous return to the heart improves and cardiac output is expected to improve.

There are advantages and disadvantages of the two main types of gastric decompression procedures. Gastric trocarization is faster to perform than orogastric tubing and, because sedation is not required for this procedure, it may be a better choice for the haemodynamically unstable patient. However, gastric trocarization does not allow the evacuation of stomach contents (fluid, food and other particles) or gastric lavage, as can be carried out with orogastric tubing.

To the authors’ knowledge, there is no study assessing these two methods of gastric decompression for initial management of GDV. The objectives of this study were to report the effectiveness of orogastric tubing and gastric trocarization, to report their complications, and to investigate any differences in complication rate between the two methods.

Materials And Methods

Records of 116 confirmed cases of GDV were retrospectively reviewed. The electronic medical record database (University Veterinary Information System, Version 4.0) at the University of Minnesota Veterinary Medical Center (UMN-VMC) was searched for all dogs diagnosed with GDV from June 2001 to October 2009. Cases were included if GDV was diagnosed via a right lateral abdominal radiograph, the method of preoperative gastric decompression was noted, and definitive surgical correction was performed at the UMN-VMC. Cases were excluded from analysis if the method of preoperative gastric decompression was not noted in the medical record.

The medical records were evaluated for the following criteria: signalment, method of preoperative gastric decompression, degree of volvulus noted in surgery, splenic laceration, splenectomy, gastric compromise treated with surgical intervention, presence of gastric perforation, aspiration pneumonia, oesophageal rupture, length of hospitalization and survival to discharge. Gastric compromise was defined as the status of the gastric wall noted at time of surgery and surgical intervention included either partial gastrectomy or gastric invagination. Degree of volvulus was divided into the following categories: none (volvulus not observed at the time of surgery), moderate (90°, 180° or 270° of volvulus) or severe (360° or 540° of volvulus). The degree of volvulus was determined intra-operatively via direct visualization and was based on the amount of de-rotation needed to return the stomach to a normal anatomical position. Aspiration pneumonia was defined as those dogs with a radiographic diagnosis of the disease.

Gastric trocarization or orogastric tubing was performed as previously described (Rasmussen 2003). Briefly, gastric trocarization was performed using a 14 gauge, over-the-needle intravenous catheter (BD Angiocath). The catheter was inserted through the aseptically prepared skin, at the area of greatest abdominal distension, and into the stomach. Lateral pressure was applied to the abdomen to facilitate evacuation of gas from the stomach.

Orogastric tubing was performed using a large-bore, silicone, orogastric tube. A roll of 7·5 cm white medical tape (3M) was used as a mouth gag in all dogs before passing the tube. Tube length was measured from the tip of the nose to the last rib; the tube was lubricated with a water-soluble lubricant (Surgilube; Fougera Pharmaceuticals) and passed through the roll of tape and into the stomach. In all dogs, water was instilled through the tube and the gavage was allowed to drain. To safely perform this procedure in the alert animal, sedation (typically a combination of a benzodiazepine and opioid) was administered intramuscularly or intravenously to facilitate passage of the orogastric tube.

The decision on which method of gastric decompression to perform first was based on clinician preference, and was not standardized between cases.

Statistical analysis was performed using chi-squared analysis (JMP version 8.0.2). Comparisons were made to determine if statistically significant associations existed between the method of gastric decompression and gastric compromise treated with surgical intervention and overall survival. A P-value of less than 0·05 was considered statistically significant.

Median age of all dogs at the time of presentation was 7·5 years (range, 0·6-15·6 years). There were 70 (60·3%) males and 46 (39·7%) females. Of the 70 males, 61 (87·1%) were neutered and 9 (12·9%) were intact. Of the 46 females, 39 (84·8%) were spayed and 7 (15·2%) were intact. Median weight was 39 kg (range, 19·5-80 kg). Median length of hospitalization was 1 day (range, 1–6 days). One hundred eleven dogs (95·7%) survived to discharge, while 5 (4·3%) dogs did not.

Of the 75 dogs in which the degree of volvulus at the time of surgery was recorded, three dogs (4%) had a 90° volvulus, 46 (61·3%) had a 180° volvulus, 16 (21·3%) had a 270° volvulus, 3 (4%) had a 360° volvulus, 1 (1·3%) had a 540° volvulus and in 6 (8%) dogs no volvulus was noted at the time of surgery. The degree of volvulus in the remaining 41 dogs was not noted in the medical record.

Of 116 dogs, orogastric tubing was performed in 31 (27%), gastric trocarization in 39 (34%) and a combination of both techniques in 46 (40%). For those dogs undergoing both procedures, the decision of which procedure to perform first was not standardized and was based on clinician preference.

General anaesthesia was not needed in any dog in order to pass an orogastric tube. Sedation was used in 47 of 77 dogs to facilitate passage of the orogastric tube. Orogastric tubing was successful in 59 (76·6%) dogs and unsuccessful in 18 (23·4%) dogs. Success was defined as passage of the tube into the stomach with visualization of gastric contents in the tube. Of the 18 cases in which tubing was unsuccessful, 2 cases were diagnosed with a severe volvulus, 9 with a moderate volvulus and in 7 cases the degree of volvulus was not listed in the medical record. Other than inability to pass the tube, no complications during orogastric tubing were encountered during tube passage or subsequent gavage. No dogs that underwent orogastric tubing were diagnosed with or developed clinical signs of aspiration pneumonia or oesophageal perforation while hospitalized.

No sedation was required for dogs undergoing gastric trocarization only. Trocarization was successful in 73 (86%) dogs and unsuccessful in 12 (14%) dogs. Success was defined as the passage of gas through the catheter. Gastric trocarization was performed on the left side in 13 dogs, on the right side in 4 dogs, bilaterally in 5 dogs and in 61 dogs the side of gastric trocarization was not listed in the medical record. No evidence of gastric leakage into the abdomen was noted at surgery in any dog undergoing gastric trocarization. Splenic laceration occurred in 1 of 85 (1·2%) dogs in which gastric trocarization was performed; however, the dog did not require subsequent splenectomy. In that case, gastric trocarization was performed bilaterally.

Splenectomy was performed in 8 of 116 (6·9%) dogs. Splenectomy was performed if vascular thrombi in the splenic vessels were noted, or if the spleen had obvious signs of ischaemia that did not resolve after gastric de-rotation and decompression. Of those dogs requiring splenectomy, orogastric tubing was performed in one, gastric trocarization in three and a combination of orogastric tubing and gastric trocarization in four dogs. Of the seven dogs undergoing gastric trocarization, the side of gastric trocarization was not listed in the medical record.

Gastric perforation was not noted in any dog undergoing orogastric tubing or gastric trocarization. Gastric compromise that required surgical intervention was seen in 13 of 116 dogs. Gastric necrosis was noted in four of these dogs, while severe gastric hyperaemia was noted in the other nine dogs. Of those 13 dogs with gastric compromise, orogastric tubing was performed in 4, gastric trocarization in 3, and a combination of orogastric tubing and gastric trocarization in 6 dogs (Table 1). Gastric resection or invagination was performed if gastric necrosis was present, or if severe gastric hyperaemia was present and the surgeon deemed it likely that the area of hyperaemia may progress to necrosis.

Table 1. Association between the method of gastric decompression and resulting gastric compromise and survival to discharge

Five dogs (4·3%) did not survive to discharge from the hospital. Of those dogs, orogastric tubing was performed in two, gastric trocarization in one and a combination of orogastric tubing and gastric trocarization in two dogs (Table 1). All these dogs were diagnosed with disseminated intravascular coagulation (DIC) before death.

Splenic laceration, gastric perforation or aspiration pneumonia did not occur in any of the dogs that underwent orogastric tubing. One dog that underwent gastric trocarization was diagnosed with a splenic laceration. Otherwise no dogs that underwent gastric trocarization were diagnosed with gastric perforation or aspiration pneumonia.

No significant difference was found between the method of gastric decompression and gastric compromise requiring surgical intervention (χ2=0·8, P=0·68) or survival to discharge (χ2=0·38, P=0·83).

Discussion

There are no published veterinary studies investigating the risks of gastric trocarization. In theory, gastric trocarization could cause splenic laceration and/or gastric perforation leading to leakage of gastric contents. Of the eight dogs in this study in which a splenectomy was performed, none had evidence of splenic laceration. All splenectomies were performed because of the presence of vascular thrombi and resulting splenic ischaemia that was noted during surgery. In the one case in which a splenic laceration was noted at the time of surgery, splenectomy was not performed. In that case, gastric trocarization was performed bilaterally. It is unknown whether the splenic laceration occurred when gastric trocarization was performed on the left side, and the spleen was positioned normally, or when gastric trocarization was performed on the right side and the spleen was malpositioned. If gastric trocarization is performed, it may be advisable to use ultrasound guidance to identify the location of the spleen before the procedure. While gastric perforation causing leakage of gastric contents was not noted in our study, the possibility of this complication remains.

Gastric trocarization was successful in the majority of cases but was unsuccessful in a few. The possible reasons for an unsuccessful outcome after gastric trocarization in this study include too small a catheter (in length or gauge), the absence of a significant amount of gas in the stomach or a failure to place the catheter into the stomach. Given the retrospective nature of this study, it is not possible to definitively state why gastric trocarization was unsuccessful in some cases. A prospective study investigating these possibilities is needed to determine the exact cause of failure of gastric trocarization.

Orogastric tubing in humans can be associated with aspiration pneumonia, oesophageal necrosis, oesophageal perforation and/or gastric perforation (Hafner et al. 1961). In theory, these risks also exist in veterinary patients. In the dogs undergoing orogastric tubing in this study, no instances of oesophageal or gastric perforation were noted at the time of surgery. In four of these cases, gastric necrosis was noted at the time of surgery. A diagnosis of necrosis was made based on abnormal serosal surface colour and palpation. In areas of necrosis, where the gastric wall is more friable, it is possible that perforation could occur with contact of the orogastric tube and the necrotic wall. All four cases in which gastric necrosis was present underwent orogastric tubing during initial stabilization. However, the location of gastric necrosis was not noted in the medical record, and it is unknown whether the orogastric tube contacted those areas.

An additional complication of orogastric tubing that can be encountered is the inability to pass the tube into the stomach, which occurred in approximately 25% of dogs in this study. In the two cases of severe volvulus, the inability to pass the orogastric tube into the stomach may have been due to rotation and subsequent narrowing of the lower oesophageal sphincter or technical error (too wide a tube, insufficient amount of lubrication on the tube, insufficient sedation) during initial stabilization. In the nine cases of moderate volvulus, inability to pass the tube may have been due to either technical error during initial stabilization, or the gastric volvulus may have partially corrected itself before surgery. In theory, a moderate volvulus (i.e. <360º) should not cause narrowing of the lower oesophageal sphincter to the point through which an orogastric tube cannot be passed. In all nine cases of moderate volvulus, gastric trocarization was performed after failed orogastric tubing. It is possible that after gastric trocarization was performed, gastric distension was relieved sufficiently such that the stomach was able to partially de-rotate. This theory is supported by the current findings in which no volvulus was noted in six dogs at the time of surgery. All these dogs were diagnosed with a GDV via radiography on admittance, and all underwent gastric trocarization during initial stabilization. It is not possible to comment on the inability to pass the orogastric tube in the seven cases in which the degree of volvulus was not listed in the medical record.

In this study, gastric trocarization and orogastric tubing were associated with low complication rates and high success rates. While neither procedure required general anaesthesia, over half of the dogs undergoing orogastric tubing required sedation before the procedure, while none required sedation before gastric trocarization. In instances of the haemodynamically unstable patient, sedation may not always be safe, and a procedure that can be done without sedation may be preferred. Furthermore, while not seen in this study, the risk of aspiration pneumonia secondary to orogastric tubing is still theoretically possible. Whether sedated or not, those patients undergoing orogastric tubing are not intubated, and thus their airway is not protected. If any gastric contents leak from the orogastric tube or are expelled from the stomach around the tube, it is possible aspiration would occur. It could be argued that the risk of splenic laceration is a reason to avoid gastric trocarization. Even if splenic laceration occurs it may not cause a clinically significant problem to the patient (as evidenced by the dog in this study in which a splenic laceration occurred but splenectomy was not required) or if it does (i.e. persistent haemorrhage from the spleen) that the patient will be undergoing immediate surgery for correction of the GDV, at which time the haemorrhage can be stopped.

It is acknowledged that there are limitations to this study, including its retrospective nature. Cases were included if GDV was confirmed with radiography and the method of gastric decompression was noted. In some cases, the medical records were incomplete and further required information was not available, most notably the degree of gastric volvulus and the location of gastric trocarization. Follow-up of the cases was not performed, and therefore the medical records were only reviewed for information gathered until survival to or death before hospital discharge.

A further limitation is that the method of gastric decompression and the order in which they were performed was not standardized and instead based on clinician preference. Without a standardized protocol for gastric decompression, there is the possibility of bias in selecting cases to perform one method over the other. In this study, approximately 40% of the cases underwent both gastric trocarization and orogastric tubing. Because both techniques were utilized in these cases, it reduces the number of cases available for direct comparison between the two techniques and decreases the overall power of the study.

The final limitation is that survival to discharge is influenced by other factors not evaluated in this study. One such factor is haemodynamic stability and the response to intravenous fluid resuscitation. Two recent studies have shown that a decrease in plasma lactate concentration in response to intravenous fluid therapy can be predictive of survival in dogs with GDV (Zacher et al. 2010, Green et al. 2011). Because of the retrospective nature of this study and that the manner of fluid resuscitation was not standardized between cases, it was not possible to investigate the effect the method of gastric decompression had on the haemodynamic status of the patient. Also, given that these patients present in varying degrees of hypovolaemic shock, it would be difficult to draw conclusions as to whether it was the method of gastric decompression that improved the haemodynamic status of the patient or if the improvement was simply a response to intravenous fluid therapy.

In conclusion, this study found minimal complication rates and high success rates of two methods of gastric decompression in this population of dogs presenting with GDV. Gastric trocarization, however, did not require sedation when compared to orogastric tubing, which may make it a better option for gastric decompression, especially in the haemodynamically unstable patient. Further prospective studies are required to determine if the method of gastric decompression affects short- and long-term mortality rates or the haemodynamic status of the patient.